The worms that invade your brain

Updated 5:32 AM ET, Tue January 20, 2015

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Photos:The worms that invade your brain

The most common form of brain tapeworm is the pork tapeworm -- Taenia solium. Taeniasis, the intestinal infection transmitted by the adult worm, is a mild condition, caused by eating undercooked pork ...

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Photos:The worms that invade your brain

... but infection with the worms' juvenile (larval) form has worse consequences as the younger worms can migrate to other parts of the body. If they enter the nervous system the worms can form cysts in the brain, which have severe consequences, including epilepsy. In the radiology image above, the cysts are identified as white lumps within the brain.

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Photos:The worms that invade your brain

The young larvael forms of Taenia solium can migrate to the brain where they burrow to form cysts. This is a brain specimen of a patient in China with the resulting condition, known as neurocysticercosis.

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Photos:The worms that invade your brain

Pigs are the primary source of contracting Taenia solium. Though pork when properly prepared and cooked is not problematic, the World Health Organization says poor sanitation and substandard slaughterhouses contribute towards transmission. The worms release their eggs in the pigs' feces, which results in more severe infection.

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Photos:The worms that invade your brain

In 2013 a British man of Chinese ethnicity was diagnosed with a tapeworm, Spirometra erinaceieuropaei, inside his brain. The 50-year old first experienced headaches four years earlier and was treated for tuberculosis. The arrows point to the mass created by the worm in his brain.

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Photos:The worms that invade your brain

After four years, the British patient returned to hospital in pain to find his brain lesion had migrated to a new region of the brain resulting in new symptoms, including seizures. His MRI scans show the tapeworm's burrowed migration through the brain over four years.

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Photos:The worms that invade your brain

The worm, seen here in gray next to a five pence piece, measured only 1cm in length yet managed to wreak considerable damage on its path through the brain.

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Photos:The worms that invade your brain

This was the first occurrence of Spirometra erinaceieuropaei in the UK but the infection is more common in China, South Korea, Japan and Thailand. This microscope image shows the worm (center) on a slide after being removed from the patient.

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Photos:The worms that invade your brain

The tapeworm has a complicated life cycle through which it infects both animals and humans. The juvenile form of the worm -- known as larvae -- are found in contaminated water as well as the flesh of frogs and snakes. Consumption of raw flesh from these animals or drinking contaminated water can lead to infection, from which the larvae can migrate to many parts of the body, including the brain. In China, the practice of using frog meat as a form of poultice to calm sore eyes or treat wounds can also cause infection.